Stern gear squeal and stiff shaft

[LittleSister]

This is not the thread about stiff shafts, squeals and stern gear that it might have been.

 

[Fr J Hackett]

This is not the thread about stiff shafts, squeals and stern gear that it might have been.

That's only because I didn't read it earlier.

 

[Tamar]

On my motorboat I have been getting an intermittent noise coming from the stern gear for the last 10 years. I have changed everything except the prop. I was told it was prop singing by an engineer that came out to listen. It's only at certain slow revs and it goes away after 1200rpm. I have done over 35k nm with it and just live with it

 

[merjan]

It is possible to have the shaft flanges perfectly in line but with the shaft out of centreline in relation to the P bracket. This excessive friction could be the squeal you are hearing.
I suspect you have improved this situation but it might still be worth checking again.

Disconnect the flanged coupling at the gear box and try moving the shaft side to side and up and down. Check the shaft is moving an equal amount in each direction . If not than adjust the mounts accordingly. They usually have slotted holes to help with this. Recheck face to face . Hopefully the shaft will now be free.

Thank you, this was "roughtly" the case, but I think this option now deserves a second careful check.

 

[merjan]

It does leave the question of what happened to the P bracket to cause the distortion in the 1st place; a significant force must have been applied.

Great question, and probably one of the previous owners of the boat knows the answer very well. Interestingly enough the P-bracket itself is bent, too. You would think the prop caught a rope or something. But the shaft centered the stern tube perfectly despite the P bracket body being off-centre. Best explanation I had so far is that the P bracket was installed wrong, and someone banged on it with a hammer until it was pointing in the right direction.

 

[merjan]

This is not the thread about stiff shafts, squeals and stern gear that it might have been.

I knew this comment would come in at some point!

 

[merjan]

On my motorboat I have been getting an intermittent noise coming from the stern gear for the last 10 years. I have changed everything except the prop. I was told it was prop singing by an engineer that came out to listen. It's only at certain slow revs and it goes away after 1200rpm. I have done over 35k nm with it and just live with it

Thank you - In general that's a real possibility but I am sure was not the prop singing: a) the shaft is difficult to turn b) the bearing squeaked even if I turned the shaft very slowly (this is now gone)

 

[merjan]

His words :



mmmmmm still think he didn't ??

Wrong terminology (to be fair, the person who gave me the idea described it as a "drift"). The stainless parts have been driven like a screw"driver" drives screws. No. hitting. happened!

 

[Refueler]

Wrong terminology (to be fair, the person who gave me the idea described it as a "drift"). The stainless parts have been driven like a screw"driver" drives screws. No. hitting. happened!

ok ... still got a 'squeal' though ...

 

[Refueler]

Great question, and probably one of the previous owners of the boat knows the answer very well. Interestingly enough the P-bracket itself is bent, too. You would think the prop caught a rope or something. But the shaft centered the stern tube perfectly despite the P bracket body being off-centre. Best explanation I had so far is that the P bracket was installed wrong, and someone banged on it with a hammer until it was pointing in the right direction.

Oh Dear ... sorry to read that.

 

[merjan]

ok ... still got a 'squeal' though ...

The squeal stopped after aligning the engine as best as I could (not to 0.004" but more like 0.007"). The problem that remains is that the shaft is difficult turn. It was so even with the coupling removed.

 

[merjan]

Latest update on this: After running the engine a bit, now I can turn the shaft by hand. I can hear some squealing as I do that, but nothing can be heard at high revs. Next I'll measure the revs, and if the engine is going up to the expected rpm under load then I will have some peace of mind.

Thank you all who responded!

 

[Simonalana]

I had this same problem. Do you have a water feed to stern tube. If so I removed pipe to check water flow and injected some stern tube grease into stern tube and that stopped the noise. I was told this should be done as a part of normal service

 

[merjan]

I had this same problem. Do you have a water feed to stern tube. If so I removed pipe to check water flow and injected some stern tube grease into stern tube and that stopped the noise. I was told this should be done as a part of normal service

By "stern tube", do you mean stuffing box? If not, and you really mean the (typically fibreglass) stern tube that the shaft goes through, I would have expected that there is no contact betwen that and the shaft. Therefore no greasing would be required. In any case, I am glad your noise issue is solved!

 

[Simonalana]

By "stern tube", do you mean stuffing box? If not, and you really mean the (typically fibreglass) stern tube that the shaft goes through, I would have expected that there is no contact betwen that and the shaft. Therefore no greasing would be required. In any case, I am glad your noise issue is solved!

No I mean stern tube I changed stern gland packing and still had the squeak but took off water feed and put in a little grease and all was good. I won't mention the feed tube breaking off at the engine end and causing a drill and re tap and new fitting but all good now